Acoustic wave device
a technology of acoustic waves and acoustic waves, which is applied in the direction of impedence networks, electrical devices, etc., can solve the problems of increasing the propagation loss of acoustic waves
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first embodiment
[0027]FIG. 6A is a top schematic view of an acoustic wave device in accordance with a first embodiment, and FIG. 6B is a schematic cross-sectional view taken along line A-A in FIG. 6A. In FIG. 6A, the SiOF film is illustrated transparently. Referring to FIG. 6A, a comb-shaped electrode 12 and reflectors 14 are located on a piezoelectric substrate 10 made of, for example, an LT substrate. The reflectors 14 are located at both sides of the comb-shaped electrode 12. The comb-shaped electrode 12 is an electrode that excites an acoustic wave. The comb-shaped electrode 12 includes an input electrode and an output electrode disposed so as to face each other, and electrode fingers of the input electrode and those of the output electrode are aligned in alternate order. The comb-shaped electrode 12 and the reflectors 14 are mainly made of Cu for example.
[0028]Referring to FIG. 6B, an oxide silicon film doped with, for example, F (hereinafter, referred to as an SiOF film 16) is provided so as ...
second embodiment
[0035]FIG. 7 is a schematic cross-sectional view of an acoustic wave device in accordance with a second embodiment. Referring to FIG. 7, a dielectric substance 18 made of, for example, an aluminum oxide film is located on the SiOF film 16. As other structures are the same as those of the first embodiment, a description is omitted.
[0036]The acoustic velocity of the aluminum oxide film is faster than that of the SiOF film. Thus, the acoustic wave energy is confined between the dielectric substance 18 and the surface of the piezoelectric substrate 10. That is to say, the acoustic wave device in accordance with the second embodiment is a boundary acoustic wave device. Therefore, the acoustic wave device of the second embodiment is able to reduce the size of the device.
[0037]As described in the second embodiment, even in a case where the dielectric substance of which the acoustic velocity is faster than that of the doped oxide silicon film is located on the doped oxide silicon film, it i...
third embodiment
[0040]A third embodiment is a fabrication method of an acoustic wave device. Before a description is given of the fabrication method of the acoustic wave device, a description will be given of an experiment conducted by inventors. An SiOF film having a film thickness within a range of 1 to 3 μm is formed on a silicon substrate under various film forming conditions by CVD, and the reflectance spectrum of the SiOF film is measured by the spectroscopic film thickness meter. In addition, the reflectance spectrum of the silicon substrate on which the SiOF film is not located is also measured. Then, obtained is a normalized reflectance calculated by normalizing the local maximum value of the reflectance of the SiOF film when the wavelength of the incident light is around 240 nm by the reflectance from the silicon substrate. Then, resonators having a comb-shaped electrode and a reflector on a piezoelectric substrate and the SiOF film having a film thickness of 0.3λ (λ is a wavelength of an...
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